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Detecting and measuring individual trees with laser scanning in Latvian forest conditions
2010
Priedītis, G., Latvia Univ. of Agriculture, Jelgava (Latvia) | Smits, I., Latvia Univ. of Agriculture, Jelgava (Latvia) | Dagis, S., Latvia Univ. of Agriculture, Jelgava (Latvia) | Dubrovskis, D., Latvia Univ. of Agriculture, Jelgava (Latvia)
Researching new remote sensing and data processing methods is very important subject in forestry. The objectives of research are to explore methods to determine single tree characteristics using LIDAR and adapt them for Latvian forest conditions. Different algorithms and mathematical relations for automatic calculation of tree species, coordinates, height and diameter at breast height are described. Within the project four different clustering methods for tree identification were evaluated. The first method's construction is based on reflection point count in certain height range. The second and third methods are searching for global and local maximums on height axis of LIDAR data collection. In the fourth method segmentation of aerial photography is done by using the user selected sample data. Tree tops were s discovered by searching similarly coloured regions. Field measurements were used for the calibration of LIDAR data and analysis. Sample plots were fitted in the study area with different species composition, age and density. The total number of measured trees in sample plots is 1844. Results show that height can be found mainly for I, II, III craft class trees with average error 2.5%. Stem diameter estimation error of pine is 28%, spruce 17%, birch 4.2% and second storey trees 5.4% using linear equations D = 0.6616*H + 4.6969 (for coniferous trees) and D = 0.7756*H + 3.7132 (for deciduous trees). Dividing trees in classes of coniferous and deciduous can be done by using near infra red photography. The total number of first storey trees identified by LIDAR is 91%, by aerial photographic method 94%.
Afficher plus [+] Moins [-]Impact of amelioration system renovation on the growth of mature forest stands
2010
Zalitis, T., Latvian State Forest Research Inst. Silava, Salaspils (Latvia) | Libiete-Zalite, Z., Latvian State Forest Research Inst. Silava, Salaspils (Latvia)
Both forestry theory and practice have proved that amelioration favours the growth of forest stands significantly. The growing stock increases even 10 times, if the amelioration system is well-functioning. Joint Stock Company Latvia State Forests that is managing half of forests in Latvia has started renovation of old amelioration systems aiming to improve the productivity of state owned forests in Latvia. In order to evaluate the impact of the renovation of the old amelioration systems, a tree ring width in 7 pine stands, 5 spruce stands and 3 birch stands was analysed. This study shows that the renovation itself has not affected the productivity of mature pine, spruce and birch significantly 3-4 years after the renovation. Authors have come to a conclusion that the reason for that could be too short observation period or particularities of a stand structure and age.
Afficher plus [+] Moins [-]Research on genetic aspects of Scots pine resistance to root rot
2010
Skipars, V., Latvian State Forest Research Inst. Silava, Salaspils (Latvia) | Baumanis, I., Latvian State Forest Research Inst. Silava, Salaspils (Latvia) | Rungis, D., Latvian State Forest Research Inst. Silava, Salaspils (Latvia)
Scots pine (Pinus sylvestris) is Latvia's most economically important tree species. It accounts for 38% of the total forest area of Latvia. One of diseases affecting P. sylvestris is root rot caused by the fungus Heterobasidion annosum, which causes large economic losses. There is some evidence of Scots pine trees with higher levels of resistance but no absolutely resistant tree clones have been described so far. Many genes encoding peptides and proteins with direct or indirect antifungal activity have been described in various plant species, but only few of them have been studied in conifers. In our study we have utilised various approaches to research genetic aspects of Scots pine resistance to H. annosum. Here we present our initial results. Initially, H. annosum infection was determined in 300 trees and in a subset of twenty seven trees representing fifteen families (progeny of one mother tree) infection levels were quantitatively characterised. Candidate-genes were selected based on previously published research. Gene copy number variation (CNV) analyses were performed on selected samples. Copy number variation polymorphism was detected for a gene encoding a thaumatinlike protein analogues of which are described as potent antifungal proteins in other plants. As increased gene copy number can lead to increased gene product amounts in cells it is possible that an increased copy number of thaumatin-like protein is beneficial to the pine tree in respect to resistance against H. annosum and other pathogens. Further experiments need to be performed to investigate this in more detail.
Afficher plus [+] Moins [-]Territorial organisation of game management in Latvia
2010
Baumanis, J., Latvia Univ. of Agriculture, Jelgava (Latvia) | Ozolins, J., Latvian State Forest Research Inst. Silava, Salaspils (Latvia)
The number of the most important game animals of artiodactyla species (moose, red deer, roe deer, wild boar) has been increasing in Latvia during the last 10 years. At the same time, the number of hunting districts where the census of these game animals is taken is also increasing, whereas the average area of the districts is diminishing. The studies show that at present the area of many hunting districts is notably smaller than the individual territory inhabited by these species. This particular study aims at establishing whether there is a relationship between the area of a hunting district on which a census is taken and the number of animals counted, as well as whether the number of animals is really increasing or the increase in the number is attributed to an increase in the census unit number. It was established that in respect of the four species there is a significant correlation between the area of the hunting district and the density of animals in the district. The number of moose and red deer may be assessed more objectively in the districts with an area exceeding 5,000 hectares. The census of roe deer and wild boars is notably influenced by the area of the territory where the census is taken, but the analysis does not explicitly show whether the number of roe deer and wild boars is under-assessed in large districts or over-assessed in the small ones.
Afficher plus [+] Moins [-]Temporal structure of middle-aged Norway spruce stands of low growth potential on drained sites
2010
Libiete-Zalite, Z., Latvian State Forest Research Inst. Silava, Salaspils (Latvia) | Zalitis, T., Latvian State Forest Research Inst. Silava, Salaspils (Latvia)
Large proportion of 30-50 years old spruce stands originated from overstocked plantations can be characterized by low growth potential and present serious problem to forest managers. Although according to legislation unproductive spruce stands can now be clearcut, possible alternative solution allowing a forest owner to remove only trees with the worst growth potential would be also welcome. To be able to recommend any silvicultural measures, information on the inner structural development of the stands is necessary. The aim of this study was to analyze temporal structure of several spruce stands that have originated from overstocked plantations and now belong to the 2nd (increased risk stands) or 3rd (unpromising stands) growth potential groups. Data for the study from seven sample plots located in Forest Research Station ''Kalsnava'' and thinned with different intensity were used. Tree diameter distribution, volume accumulation patterns and tree mortality were analyzed. Correlation between tree diameter and tree diameter difference in the observation period from 2000 to 2006 was weaker than in the observation period from 2006 to 2009, indicating further decline of growth potential. In most cases the major part of the volume was accumulated in the middle of the diameter class distribution. For most of the trees one or both sawlogs were of good or average quality. In order to develop optimal and profitable stand management model, the effect of different thinning methods in spruce stands of low growth potential should be studied in the future.
Afficher plus [+] Moins [-]Participatory approaches to investigate breeding objectives of livestock keepers
2010
Duguma, G. | Mirkena, T. | Haile, Aynalem | Iñiguez, L. | Okeyo Mwai, Ally | Tibbo, Markos | Rischkowsky, Barbara A. | Sölkner, Johann | Wurzinger, Maria
There are distinct breeds suitable for diverse purposes in the different production environments or ecological zones. Farmers in different production systems have different trait preferences and the strategies followed by them are also as diverse as the agro-environments within which they operate. In order to design a viable breeding plan, farmers’ preferences for the different traits need to be investigated. In this paper available tools and methods for defining livestock breeding objective traits are described, discussed and comparisons among them are made. The reviewed tools were: participatory rural appraisal (PRA), choice experiments, ranking of animals from own flock/herd and ranking of others animals. Each methodology may be appropriate to specific situation; however, it is recommended that a combination of approaches be used to precisely capture the breeding objective traits of livestock producers. Elucidation of objective traits using the tools with active involvement of producers can result in appropriate livestock genetic improvement that is well grounded in practical reality and truly reflects owners’ preferences.
Afficher plus [+] Moins [-]Economic analysis of animal disease control inputs at farm level: the case of trypanocide use in villages under risk of drug resistance in West Africa
2010
Affognon, Hippolyte D. | Randolph, Thomas F. | Waibel, H.
This paper presents an economic analysis of the use of drugs (isometamidium and diminazene) in controlling African Animal Trypanosomosis (AAT), a serious disease of cattle and small ruminants in villages that exhibit resistance to isometamidium in Burkina Faso and Mali in West Africa. The study applies a production function framework integrating a damage control function to assess the short term productivity effect of trypanocide use under different epidemiological conditions. We found that the marginal value products of isometamidium in all epidemiological conditions, and the marginal value product of diminazene in high-prevalence-high-resistance conditions are positive and greater than one revealing an underuse of trypanocidal drugs in those conditions. The economical optimum level of isometamidium is far larger than the current use level. In a strict economic interpretation, this implies that in the short term cattle farmers could increase the profitability if they increase trypanocide input beyond current levels. On the other hand, if the use of trypanocide increases, cattle farmers will also be more likely to experience future losses from trypanocide resistance. In this paper we demonstrated the feasibility of applying the damage control framework for measuring the productivity of veterinary therapeutic drugs at farm level in poor African countries.
Afficher plus [+] Moins [-]Factors influencing the trade of local chickens in Kampala city markets
2010
Emuron, Nathan | Magala, Henry | Kyazze, Florence B.||Kugonza, Donald R.||Kyarisiima, Connie C. | Kyazze, Florence B. | Kugonza, Donald R. | Kyarisiima, Connie C.
A study was conducted to determine the factors influencing the supply of live indigenous (local) chickens in Kampala city markets in December 2008. A total of fifty local chicken traders were randomly selected from five markets to respond to a structured questionnaire. Chicken trade was generally informal. Local chickens were mainly marketed alive in Kampala markets and the main customers were piecemeal consumers. The majority of the traders (52.9%) obtained local chickens from Eastern Uganda. Chickens were transported to markets in passenger vehicles, on motorcycles and on lorry trucks that were carrying cattle and other agricultural produce. This mode of transport sometimes caused injuries and bird mortality. Fifty percent of the traders obtained the chickens from middlemen while 46% of the traders personally bought the birds from rural farm households. Chicken trade was the major source of household income to 72.7% of the chicken traders and many of the traders had secondary sources of income. During peak seasons, the traders could sell an average of 120 birds per week per person. Local chicken marketing involved traders of varying levels of education (with a mean of 9.5 years of formal education). The number of local chickens traded per week was positively correlated (P<0.01) with the level of education of the traders. The demand for these chickens was highest in the festive months of December and April; and lowest in February and March. The cost of local chickens was more than twice as much as that of exotic chickens. Most traders (56.7%) perceived taste to be the basis for consumers’ preferential demand for local chickens in preference to exotic chickens. The major constraints in the marketing of local chickens in Kampala city markets were identified as high mortality rates/chicken diseases (43.5%), costly transport (22.4%), and irregular demand (15.3%). The study revealed that there was a high potential for the development of local chicken trade in Uganda. Designing solutions for the constraints of local chicken marketing would act as a tool for poverty alleviation not only to the rural chicken farmers but also the traders.
Afficher plus [+] Moins [-]Role of traditional enclosures on the diversity of herbaceous vegetation in a semi-arid rangeland, southern Ethiopia
2010
Angassa, A. | Oba, G. | Treydte, A.C. | Weladji, R.B.
Grazing management and seasonality strongly influence the recovery potential of herbaceous vegetation in semi-arid rangelands of southern Ethiopia after history of heavy grazing. We investigated effects of management (enclosures versus grazed landscapes), age of enclosures and seasonality related to rainfall (i.e., independent variables) on herbaceous biomass, grass basal cover, herbaceous species abundance, species richness and diversity in a savanna rangeland of southern Ethiopia. We further assessed the relationship between the herbaceous biomass and species richness. Management significantly affected most of the herbaceous response variables (i.e., comparing enclosures and open grazed). Herbaceous biomass, grass basal cover, herbaceous species richness and diversity were greater in enclosures than in grazed areas. Rainfall was also influential on herbaceous biomass, grass basal cover, abundance of herbaceous species, herbaceous species richness and diversity. Herbaceous biomass, abundance and diversity did not however vary with the age of enclosures, while herbaceous species richness appeared to decrease as the age of enclosures advanced. Grass basal cover initially decreased and later on increased with the age of enclosures, so that the older enclosures disclosed improvement of grass basal cover.
Afficher plus [+] Moins [-]Rangeland dynamics in South Omo Zone of Southern Ethiopia: Assessment of rangeland condition in relation to altitude and Grazing types
2010
Terefe, A. | Ebro, A. | Tessema, Z.K.